Electric valve converting system



June 7, 1938. c. c. HERSKIND ELECTRIC VALVE C( JNVERTING SYSTEM Filed March 20, 1937 To CONTROLLER TO CONTROLLER I nvntor Carl C. Hjrs fwd, .1: 1 7 9 His Attorney.

Patented June 7, 1938 UNITED STATES PATENT OFFICE ELECTRIC VALVE CONVERTING SYSTEM York Application March 2., 1937, Serial No. 132,152

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My invention relates to electric valve converting systems and more particularly to such systems suitable for transmitting energy between direct current circuits, one of which has a constant current characteristic.

An. electric valve converting system suitable for transferring energy between direct current circuits, one of which has a constant current characteristic, is disclosed in United States Letters Patent 1,961,080, granted May 29, 1934 upon the application of Camil A..Sabbah, for improvements in Electric valve converting systems. Such systems utilize an energy storage and transfer device comprising a multi-legged reactor provided with a single inductive winding on each leg thereof, and having associated capacitors each connected across at least a portion of said inductive windings to' maintain the total magnetomotive force oi the core structure and that of each leg substantially constant. In my copending application Serial No. 89,599, flied July 8, 1936, there are disclosed numerous improved.

electric valve converting systems of this type in which the multi-legged reactor is provided with a plurality of inductive windings on each leg thereof, and in which one winding of each leg is provided with an associated capacitor.

In certain instances where the constant current circuit supplies energy to an inductive load, such as for instance that provided by a plurality of electric motors, it is desirable to provide the electric valve converting system with a suitable control circuit which will permit obtaining certain desired operating characteristics. Such an arrangement would be particularly desirable where an electric locomotive having a plurality of motors is to be operated from a high voltage direct current trolley.

It is, therefore, an object of my invention to 4 provide an improved electric valve converting system for transferring energy between two 'direct current circuits which will overcome certain limitations of the arrangements of the prior art, and which will be simple and reliable in opera- 46 tion.

It is a further object oi my invention to provide an improved electric valve converting system for transmitting energy between direct current circuits in which the output of the sys 50 tem is controlled in accordance with increases inthe constant current voltage.

The novel features which I believe to be characteristlc of my invention are set forth with particularity in the appended claims. )[y invention 55 itself, however, both as to its organization and method of operation, together with further ob- Jects and advantages thereof, will be better understood by reference to the following description taken in connection with the accompanying drawing in which the single figure shows an elec- I tric valve converting system embodying my invention which is suitable for transferring energy between constant potential and constant current direct current circuits.

Referring now more particularly to the single 10 figure of the drawing, there is illustrated an arrangement embodying my invention for transferring energy from a constant potential circuit iii, which may be a high voltage trolley system, and a constant current direct current circuit II it which supplies energy to an inductive load comprising a plurality of motors l2. This system is provided with an energy storage and transfer device comprising a three-legged magnetic core structure II indicated in the drawing by a dotted 20 line rectangle. Each of the legs H, II and ii of the core structure I! is provided with a pair of inductive windings H, II; I9, 20; 2|, 22, each pair of inductive windings being provided with energy storage devices which may be in the as form of the capacitors 22, and 2B. These capacitors 22, 24 and 25 may be connected in parallel with the inductive windings ll, II and II, respectively, or at least across portions thereoi, so as to form energy storage circuits. One to terminal of each of the inductive windings ll, II and 2i is connected through an inductor 28 and a circuitbreaker 21 to one side of the direct current circuit l0. One terminal 0! each of the in ductive windings ll, 20 and 22 is'connectcd 35 through an inductor 28 to one side of the direct current circuit II. An electric valve apparatus 29 provides a, controlled electric discharge path for each of the inductive windings I1 to 22, inclusive. While electric valve apparatus 29 is shown as being of the single cathode-multianode type, this electric valve apparatus may be any of the several types well known in the art, although it is preferable to utilize electric valves of the type containing an ionizable medium and which are provided with a control or starting electrode whereby the discharge paths between the anodes and cathodes may be controlled. In the arrangement shown, each of the inductive windings II to 22 is connected to a different so one of the anodes III to 2!, respectively, of the electric valve apparatus 29, the cathode of which is connected to both direct currentcircuits II and II. The control electrodes of the anodes ll, 22 and 2| are controlled from a source of al gs paratus is.

j, motor is may he determined thereby.

' between the negative side oi the direct our ternating' current comprising an alternating cur-- rent generator 36 through a phase shifting device 3i, and the primary and secondary windings 86 and 39 of a delta to star-connected control transformer. The remaining control electrodes of the anodes 3!, 33 and 35 are energized from the same source of alternating current 36 through the primary and secondary windings 4t and ll of an= other delta to star-connected control tranc former. The midpoint of the secondary wind ing ll connected directly to the cathode of the electric valve apparatus 28, whereas the midpoint of the secondary winding 39 is connected through. a resistor 42 to the cathode of the ep- The purpose or the resistor 42 will Tecoine apparent in the description of the operation of the system. The alternating current generator 35 is driven by a motor t3 which may he energized from a suitable source oi' direct cur rent N. The direct current motor 43 is provided with two fields 45 and it. The field to arranged in shunt relation to the armature through resistors 4i and 48. The resistor i may Ye adjustable so that the normal speed or the A pair of conductors to are connected across the current circuit 5 l and supply energy through the contacts of a relay 58 to the field eluding d8 of the motor 43. The resistor t8 may he short circuitet'i through the contacts or" a relay lit. The

relays and iii are connected in series to he energized from a controller which he or" the types commonly used in controlling electrio locomotives. A conductor is conn cte circuit 45 and one terminal or" the resistor 33. The other terminal of the resistor Q53 is connected to one or" the contacts of each of the relays 5t and 54. The relay 5% is connected. across the conductors to and so arranged as to operate in response to a predetermined voltage appearing across the direct current circuit ii. The relay 54 is arranged to he energised from same controller which controls the energiaation of the relays and 58. The operation of either or relays 53 or 54 serves to connect by means of conductor 55 the positive terminal of the direct current circuit 84 to one side of the resistor 62, thereby placing a high negative bias upon the control electrodes of the anodes 30, 32 and 34. This negative bias is suflicient to prevent the alternating current supplied from the generator 36 through the phase shifter and the transformer windings 38 and 39 from rendering these electric discharge paths conductive.

The operation of the electric valve converting system will first he described without reference to the sequence of operations which may he pro vided by the relays of the control circuit. In operation, neglecting leakage reactance between the windings associated with each leg of the core structure l3, the windings and capacitors assoelated therewith serve to maintain the total magnetomotive force in that of each of the legs or the magnetic core structure l3 at a substantially constant value. Each of the electric discharge paths of the anodes 30 to 35 and the cathode of the electric valve apparatus 29 is conductive for 120 electrical degrees of each cycle, these discharge paths becoming conductive in a predetermined sequence at a frequency equal to that of the alternating current supplied by the alternat lng current generator 36. In order to operate this system properly, the phase relation between the grid excitation of the valves 30, 32 and 34 and the valves 3!, 13 and 35 must be such that the valve connected to the winding of the corn stunt current circuit becomes conductive in advance oi the valve connected. to the corresponding winding associated with the constant potential circuit. n the excitation oi the two paths or valves, as for anodes 3G and 35, will lie between any value lust greater than Zero and slightly less than 186 degrees. The phase shifting device 31 provides the necessary means for obtaining this phase differ ence and also can he used as a control for determining the amount of energy transferredbetween the two direct current circuits. In general, the voltage relation and power transfer relation be tween the two direct current circuits is dependent upon the ratio between each pair of windings on each or" the core structure l3; the sire of the capacitors 23 to 25, the phase relation. i10 tween the excitation of the groups of control electrodes for the anodes til, 32, 34 and Si, 33, 35, and the frequency of the alternating current potential applied to the control e ectrodes of the various anodes as derived "rorn the alternating current generator till. i 2 functions performed in the operation the sy by the three-legged core structure iii, the windings ii, iii, ll the associated capacitors 2t, 2t 25 perhaps will he cla one cycle or operation of the electric clurge paths between the anodes 3G 3i and the cathode of the electric valve apparatus 29. 1" we tor example, the grid excitation supplied to the control electrodes of the anodes 30 and ti differs by phase difference of 126 degrees, the anode ill will he conductive for 120 electrical degrees, while the anode 30 remains nonconduc tive. it is assumed that the capacitor 23 has. been charged to a certain potential by a previous opera ion, and that this now discharges into the it so that by magnetic coupling with the winding is energy is supplied to the anode 3!. at the end or the period of conductivity of the anode ill, the anode 30 becomes conductive and the anode 3!! now remains nonconciuctive for 240 degrees. Thus the current transmitted by the anode 30 serves to store energy in the capacitor during the period of conductivity of this anode. [it the end of the period of conductivity of this anode 30, the current is transferred from this anode to one of the other anodes 32 or 3 and during the next 120 electrical degrees the anodes 36 and 3i looth become nonconductive. During the period when both these anodes are nonconductive, the capacitor 23 discharges into the transformer winding l] in order to maintain the required magnetomotive force in this transformer winding and in so doing the electrical charge of the capacitor reverses in polarity so that it now has the proper polarity to supply power to the anode 3i when this anode is again permitted to become conductive. From this it is believed that it will be apparent to those skilled in the art that the capacitors 23, 24 and 25 not only provide commutating potentials to cause the transfer of current between the anodes an, 32 and 34, but also operate as energy storage devices to supply current to the anodes 3|, II and 35. l

The operation as provided by the relays 50, 5|, 53 and 54 and a suitable controller will now be described. If it is assumed that the electric locomotive is at a standstill, the initial operation of the controller will connect all of the motors l2 in series relation across the direct current circuit I I. In order to obtain a high starting torque for themotors, energy must be supplied to the control electrodes of the "anodes SI, If and u at a frequency higher than normal operation would require. The initial adimtment of the controller causes the relay II to open its contacts,

thereby removing the high negative bias from,

the control electrodes of the anodes 8., I2 and 84, permitting them to become energized from the alternating current generator I. Initial operation of the controller also causes relay II to close its contacts, thereby connecting the field winding 40 across the direct current circuit ii, and the relay II to open its contacts, thereby inserting the resistor I in series with the fleld winding ll which causes the field to beweakened, thereby resulting in an increased speed of the motor 48. For the purpose of explanation, it

,may be assumed that the motor now speeds to approximately five times normal speed so that it comprises an alternating current having a frequency flve times'that of the normal frequency upon the grids of all of the anodes, and hence the output current of the converting systern will be increased from for example, an original value of 40 per cent to a value of 200 per cent. If this high frequency of the alternating current generator were to be maintained, the electric valve converting system would deliver a constant current of 200 per cent as the voltage on the motors I! increased. In order to prevent this voltage from rising above a safe value,-the ileld supplied by the fleld winding 46 .from the direct current circuit ll operates in response to voltage increases of this circuit ii to decrease the operating speed of the motor 0. The result is that the motors I! come up to speed and arthey do so the frequency of the alternating current generator II decreases so that at normal speed of the series connected motors l2, the electric valve converting apparatus operates at the desired normal rating. Whenever the voltage across the direct current circuit ll reaches a predetermined amount, which may be assumed to be a normal voltage for this circuit, the relay ll operates to close its contacts and to connect the direct current source 44 across the resistor 42, thereby preventing the anodes ll, 82 and 84 from conducting. Thus the motorman of the locomotive will then shift his controllerto the next position which connects the motors II in series-parallel relation and again the same sequence of operation of the relays II, II and it occurs, so that for this series-parallel connection a high output is obtained across the direct current circuit II which decreases as the motors I! come to their newspeed value. When this new speed value is reached, the voltage across the direct current circuit II will again be such that the relay is will operate. thereby indicating to the motorman that the controller should be moved to a new position which will connect all of the motors I! in parallel. Again the relays and the direct current motor I operate in a similar sequence until the voltage across the direct current circuit ll increases to such a point as to cause the relay 53 to operate. The relay II will now continue to operate to open and close its contacts, thereby maintaining the voltage across the direct current circuit Ii within certain predetermined limits. If it is desired to stop the locomotive or reduce its speed, any retroactive movement of the controller will cause the-relay It to operate, thereby preventing the anodes ll, 32 and 34 from becoming conductive..

, While I have shown and described my invention in connection with certain specific embodiments it will, of course, be understood that I do not wish to be limited thereto, since it is apparent that the principles herein disclosed are circuit comprising an energy storage and transfer device provided with a plurality of controlled electric discharge paths, the method which comprises initially rendering conductive said electric discharge paths at a relatively high frequency and subsequently reducing the frequency at which said electric discharge paths are rendered conductive in accordance with an electrical condition of said constant current circuit.

2. In an electric valve converting system for transferring energy between a constant potential direct current'source and a constant current load circuit comprising an energy storage and transfer device provided with a plurality of controlled electric discharge paths, the method which comprises initially rendering conductive said electric discharge paths at a relatively high frequency, subsequently reducing said frequency at which said electric discharge paths are rendered conductive in accordance with an electrical condition of said constant current circuit, and rendering said electric valve converting system nonconductive in accordance with a predetermined electrical condition of said constant current circuit.

3. In an electric valve converting system for transferring energy from a source of constant potential direct current to a plurality of load devices comprising a controlled electric valve converting system for converting direct current of constant potential to constant current direct current, the method which comprises arranging said load devices in series relation across said constant current circuit, initially rendering conductive said electric valve converting system at a relatively high frequency, and subsequently reducing the frequency of the conductivities of said electric valve converting system proportionately to increases in an electrical quantity in said load circuit.

4. In an electric valve converting system for transferring energy from a source of constant potential direct current to a plurality of load devices comprising a controlled electric valve converting system for converting direct current of constant potential to constant current direct current, the method which comprises arranging said load devices in a predetermined relation with respect to said constant current circuit, initially rendering conductive said electric valve converting system at a relatively high frequency, reducing the frequency of the conductivities of said electric valve system proportionately to increases in the voltage appearing across said load devices until a predetermined value is obtained, thereupon rearranging said load devices in a different circuit relationship with respect to said constant current circuit, rendering conductive said elec= tric valve converting system at a relatively high frequency, and reducing the frequency of the conductivities of said electric valve converting system proportionately to increases in an electrical quantity appearing in said load circuit until a predetermined value is obtained.

5. In an electric valve converting system for transferring energy from a source of constant potential direct current to a plurality of load devices comprising a controlled electric valve converting system for converting direct current of constant potential to constant current direct current, the method which comprises arranging all of said devices in series relation across said constant current circuit, initially rendering conductive said electric valve converting system at a relatively high frequency, reducing the frequency of the conductivities oi said electric valve converting system proportionately to increases in an electrical quantity in said load circuit until a predetermined value is obtained, rearranging said load devices in series-parallel relationship, rendering conductive said electric valve converting system at a relatively high frequency, reducing the frequency of the conductivities of said electric valve converting system proportionately to increases in an electrical quantity appearing in said load circuit until a predetermined value is obtained, rearranging said load devices in parallel circuit arrangement, rendering conductive said electric valve converting system at a'relatively high frequency, reducing the frequency of the conductivities of said electric valve convert-= ing system proportionately to an electrical quantity appearing in said load circuit until a predetermined value is obtained, and rendering nonconductive said electric valve converting systern whenever a predetermined electrical condition of said circuit is obtained. v

6. An electric valve converting system for transferring energy between constant potential and constant current direct current circuits comprising an n-legged core structure having a pair of windings on each leg, an energy storage device for each leg associated with one of the windings thereon, an electric discharge means providing a controlled electric discharge path for each of said windings, means for interconnecting one of the windings on each of said legs together with its associated electric discharge path to one of said direct current circuits and means for connecting the other of said windings on each of said legs together with its associated electric discharge path to theother of said direct current circuits, a control circuit for said electric discharge paths, means for supplying energy to said control circuit comprising a source of alternating current variable in frequency, and means responsive to the voltage across said constant current direct current circuit for reducing the frequency of said alternating current source in proportion to an increase in said constant current voltage.

7. An electric valve converting system for transferring energy between constant potential and constant current direct current circuits comprising a polyphase core structure having two groups of inductive windings, a plurality of energy storage devices associated with one group of said windings, electric discharge apparatus providing a controlled electric discharge path for each of said windings, means for connecting one group of windings together with its associated electric discharge paths across one of said direct current circuits, means for connecting said other group of windings together with its associated electric discharge paths across another of said direct current circuits, a control circuit for said electric discharge paths, a source of alternating current for said control circuit, means for causing said source to operate initially at a high frequency, and means responsive to the voltage across said constant current direct current circuit for reducing the frequency of said alternating current source in accordance with increases'in voltage in said circuit.

8. An electric valve converting system for transferring energy from a constant potential direct current source to a constant current direct current circuit comprising an n-legged energy storage and transfer device having a pair of windings on each leg thereof, electric discharge apparatus providing a. controlled electric dis charge path for each of said windings, means interconnecting one of said windings of each leg together with its associated electric discharge path to one of said direct current circuits, means interconnecting the remaining windings with their associated electric discharge paths with the other of said direct current circuits, 9. control circuit for said electric discharge paths, asource of alternating current variable in frequency for energizing said control circuit, means for supplying to said control circuit alternating current having a relatively high frequency, means responsive to the voltage of said constant current circuit for reducing the frequency of said alternating current in accordance with increases in load voltage in said direct current circuit, and means responsive to a predetermined voltage of said alternating current circuit for rendering non-conductive said electric discharge apparatus.

9. An electric valve converting system for transferring energy between a high potentialconstant potential direct current circuit and a low potential constant current circuit comprising an n-legged energy storage and transfer device provided with a plurality of windings on each of the legs thereof, electric valve apparatus protric discharge path to said constant potential circuit, means for connecting the remaining windings together with their associated electric discharge paths to said constant current circuit, a control circuit for said electric discharge paths, an alternating current generator for supplying current to said control circuit, an electric motor for driving said alternating current generator, means for supplying field excitation to said elec tric motor, means for initially reducing the field supplied to said electric motor, and means responsive to the voltage of said constant current direct current circuit for subsequently controlling the field excitation of said motor.

10. An electric valve converting system for supplying constant current direct current to an inductive load from a constant potential direct current source of energy comprising a multilegged energy storage and transfer device having a pair of windings on each of the legs thereof,

current circuits, a. control circuit for said electric discharge paths, an alternating current generator for energizing said control circuit, a motor for driving said alternating current generator, said motor being provided with two field windings, means for supplying energy to one of said field windings, means for reducing the energy normally supplied to said field winding, and means interconnecting said other field winding so as to be energized from said constant current circuit.

CARL C. HERSKIND. 

